Photographic stripping film



Dec. 18, 1945. G, LANE 2,391,171

PHOTOGRAPHI O STRIPPiNG FILM Filed June 7; 1941 FIG.

T/N. LULOSE ESTER.

PAPERv CHILL ED STEEL ROLL COTTON ROLL GELAT/N I ll PAPER /0 GEROULD TLANE 1 N V EN TO R BY 2 mm A TTORNE YS Patented Dec. is, 1945 PHOTOGBAPHIO STRIPPING FILM Gerould '1'. Lane, Rochester,'N. Y., assignor to Eastman Kodak Company, Rochester, N. E, a corporation of New Jersey Application June 7, 1941, Serial No. 397,093

4 Claims.

I This invention relates to photographic material and particularly to a photographic stripping film.

Photographic stripping film is generally understood as being a photographic material in which one portion is stripped from another portion before or after the formation 'of a photographic image in the sensitive layer of the material. It is frequently desirable that the portion of the film carrying the photographic image be as thin and as flexible as possible, and in order to support this portion during some of the manipulative operations, it is attached to a temporary support of film or paper.

Most photographic stripping material canbe separated only in the wet state, or if it is separable in the dry state, is of complex nature and expensive to manufacture. Dry stripping photographic material has not hitherto been widely used because of the difilculty of obtaining satisfactory and economical material.

It is therefore an object of the present-invention to provide a dry stripping photographic material having satisfactory properties for use in the photographic trade. A further object is to provide a simple photographic stripping material which can be made economically. Other objects will appear from the following discussion of my invention.

These objects are accomplished by applying to a suitably sized photographic paper stock a wax layer which is calendered to a smooth surface, andapplying the permanent support of the stripping film to this calendered wax layer.

In the accompanying drawing Fig. l is a sectional view of a stripping material made according to my invention (the various layers not being in proportion as to thickness) and Fig. 2 is a view partially in section showing the method of calendering the wax surface of the temporary support preparatory to coating the permanent support on it.

In its broad aspects my invention comprises to any flat surface such as a glass, metal or wood surface. The emulsion may be exposed before or after the permanent support is stripped from the wax layer.

A preferred form of my invention comprises a temporary base of photographic paper stock sized with gelatin and coated with a water emulsion of carnauba wax. The wax surface is calendered to a smooth finish and a coating of cellulosenitrate solution is applied. 7 This permanent support' is subbed and emulsion coated with a lightsensitive photographic emulsion of the desired type. The various aspects of the preferred form of my invention will now be described in greater detail.

double-weight photographic paper stock. It

should have a limited amount of fuzziness'so that I the paper fibers do not penetrate the gelatin and wax coatings later applied and prevent even stripping.

The gelatin coating applied to the paper base may consist of a gelatin solution containing approximately 7% gelatin and having 36 grains of chrome alum crystals added per pound of gelatin. This gelatin solution may be applied by brush application at F. and at this concentration the coverage is about 2 grams of gelatin per souare meter of paper surface. Concentrations of gelatin solutions as low as 5% have been used which have given satisfactory results. However, extremely low concentrations, for example those which give a coverage of 0.3 gram of gelatin per square meter of paper, are not satisfactory.v Higher concentrations are inclined to produce curl in the paper. The object of the gelatin coating is to cover the surface fibers of N the .paper evenly to prevent their sticking into the wax layer and into the permanent ce'llulose" nitrate support since this would increase 'adhe I sion between the layers and cause uneven strip ping.

The wax coating is prepared from an emulsion in water of a suitable wax such as camaubawax.

This is applied over the gelatin coating with the brush type application at room temperature.

The emulsion of carnauba wax is prepared by adding 30 pounds of wax to 300 pounds of water just at the boiling point. When it is melted 1.16 pounds of sodium hydroxide are added with The emulsion is then put constant stirring. through a colloid mill and further diluted with 200 pounds of water. The finished emulsion is==*,;

approximately 6% wax and has a coverage of;

- a surface sufllciently incompatible with the nitrocellulose permanent support so that the permanent base may be stripped from it. The wax layer, however, must be calendered before applying the cellulose nitrate to it. If the nitrate coating is applied to the wax surface uncalendered, the stripping results are unsatisfactory.

' Adhesion is greater on some portions of the sur-' face than on others presumably because of the difficulty in securing an absolutely uniform spread. This inequality in adhesion leadsto tearing the thin permanent support during the stripping operation. a

The calendering operation is carried out by passing the paper having the wax coating down, between a cotton roll and a hilled steel roll; the chilled steel roll faces the wax surfaces and runs at a. speed about 2 times the speed of the cotton roll. This operation levels out thewax surface and provides uniform ease of stripping. It is at this point that the excess of wax would appear as an accumulation on the steel roll and prevent a satisfactory polishing of the surface. It is essential, therefore, that the amount of wax should be kept within proper limits.

The permanent support which carries the semitive emulsion is preferably a plasticized cellulose nitrate layer. The preferred thickness of this suppo t is about .0004 inch although it may be as low as .0003 inch. A suitable nitrate would be one which has an alcohol solubility of 30 to 100%,

layer It and the wax layer l2. Over the wax layer there is a cellulose ester permanent support layer l3 followed by a gelatin subbing layer It and the emulsion layer It.

Fig. 2 illustrates the method of calendering the wax coating. As shown therein the paper It containing the gelatin coating II and .wax layer I2 is passed in the direction indicated by the arrows a viscosity of 2 to 5 seconds (dropping ball meth- 0d) and a nitrogen content of 11 to 12%. This is applied ,as a 6-7% solution in a solvent mixture comprising 85% methyl alcohol and 15% acetone to which has been added 25% of the weight of. the

nitrocellulose of castor oil. Application is preferably made to the waxed support from animmersion type hopper. It is highly desirable that this permanent base be as thin as :possible in.

order to bring the photographic image on the finished material as close as possible to final support on which the material is applied.

The gelatin sub applied to the cellulose nitrate following composition:

Per cent Gelatin 1 Water 10 Acetic acid -1 0.5 Methyl alc 88.5

The emulsion applied as a final coating may be of any suitable type but is preferably a high con.-

trast superspeed gelatino silver halide emulsion to which has been added starch as a matting material. This matting material enables the image base may be a sub of the usual type having the between a set of rolls. The roll it is an idler roll which keeps the material in contact with a cotton roll 11. Passing around the roll I! thematerial comes in contact with a chilled steel roll 18 which rotates at about 2 times the-speed of the cotton roll H. The wax surface '12 is in contact with the chilled steel rolll8 and since the roll ll moves more rapidly than the material passing beneath this roll, the wax surface is spread and calendered to a high degree of smoothness. By the selection of the proper concentrations of the various solutions, it is easily possible to prepare a material which has the right degree of adhesion between the various layers. It is by using gel and wax layers of the proper thickness and by the polishing technique outlined above that correct stripping characteristics may be obtained.

The stripping material prepared according my invention separates cleanly from the perma nent support without preliminary softening or without tearing or distortion of the film. This material may be used in the photomechanical arts or it may be used as a mask layer when applying to multi-layer colored film. It also finds application in the automotive and aircraft industries for the preparation of templates. When .used in this way the stripped material may be applied to a material used in the production of templates, emulsion side down or base side down. It may be necessaryto provide a, suitable adhesion layer for afllxing the stripped material to the metal or other material from which the template is made. The stripped material may be exposed before or after application to a metal sheet in this way.

The use of my material in the preparation of templates makes it desirable that the stripped material be as thin as possible. I find that a highly desirable film made by my process has a thickness of approximately .0006 to .0009 inch. The controlling minimum is the thickness below which materials cannot be handled when transferring is made. The plasticizer such as castor oil in the film base is important in order to prevent separation at the edges of the cut during cutting or punching of the template. Unplasticized materials not only separate but appear to retract from the edges of the cuts.

The material prepared according to my invention may be used in other ways not herein specifically mentioned and it will be understood that my invention is to be taken as limited only by the scope of the appended claims.

What I claim is: i

1. A photographic 'dry stripping film consisting, in order, of a paper temporary support havinga gelatin coating thereon, a calendered wax layer consisting of approximately 1.8 grams of wax per square meter of paper surface, a. cellulose nitrate permanent support, 'a gelatin sub, and a sensitive emulsion layer,

2. A photographic dry stripping film consisting, in order, of a paper temporary support having a gelatin coating thereon, a calendered carnauba wax layer consisting of approximately 1.8 grams of wax per square meter of paper sura cellulose nitrate permanent support, a gelatin sub, and "a. sensitive emulsion layer.

4. The method of making a photographic stripping paper which comprises coating a layer of gelatin on a paper support, emulsifying a proportion of approximately 30 pounds of carnauba wax in approximately 300 pounds of water to produce an emulsion containing approximately .6% waxand coating the emulsion on the gelatinlayer, calendering the resulting wax layer to render it smooth, applying a layer of plasticized cellulose nitrate to the calendered wax layer, and applying a gelatin sub and an emulsion layer to m the cellulose nitrate layer. v

GEROULD T. LANE. 

